Sirocco (Scirocco)

The term Sirocco (sometimes also spelled Scirocco) is an all-inclusive name given to hot and subsequently humid southeast to southwest winds originating as hot, dry desert-air over Northern Africa, flowing northward into the southern Mediterranean basin.

Siroccos occur in advance of surface and upper level depressions moving eastward across the southern Mediterranean Sea or northern Africa. These cyclones originate either over North Africa or sometimes south of the Alps, primarily in the Gulf of Genoa in the latter case.

Depending on where you are, the Sirocco is inhibiting substantially different characteristics and has many different local names, too. Along the northern African coast the hot air originates directly from the Sahara desert, producing hot, dry and dusty conditions. Visibility becomes very poor and the fine blowing dust might result in danmage to instruments and equipment. On rare occasions the Sirocco is picking up enough dust and sand to produce even sandstorms.

However, the term Sirocco is not used in North Africa, where it is called chom (hot) or arifi (thirsty);
Simoom in Palestine, Jordan, Syria, and the desert of Arabia; Ghibli (or Chibli, Gibla, Gibleh) in Libya; Chili (or Chichili) in Tunisia and S Algeria;
Khamsin (or Chamsin, Khamasseen) in Egypt and around the Red Sea and Sharavin Israel.

As the air travels northward across the Mediterranean Sea, the Sirocco picks up much moisture because of its high temperature, and reaches Spain (known as Leveche, Solano, Jaloque or Xaloque), Portugal as Xaroco, France as
Marin, Malta, Sicily, southern Italy as Scirocco, Croatia as Jugo and even Greece as a very enervating, hot, humid wind. In some parts of the Mediterranean region the word may be used for any warm oppressing southerly wind, often of foehn type. For example, in the extreme southwest of Greece a warm foehn crossing the coastal mountains is named Sirocco di Levante and a sirocco wind on Madeira and the Canaries is known as Leste.

As it travels northward, it causes clouds, fog and rain over northern Mediterranean areas. The sweltering, sultry and close waether during an Sirocco event causes headaches and insomnia for many. The hot humid wind causes overnight temperatures of 30&deg;C and above, while thermometer may well reac 40&deg;C during daytime. Extreme temperature differences (up to 20&deg;C) may occur with the following cold front and its dust may reach even Britain and northern Europe.

Sirocco events tend to occur year-round without a favored month or season. However, strong gale-force siroccos are most common during the spring. The average duration of continuous gale force winds during a Scirocco is 10 to 12 hours and occasionally as long as 36 hours. The onset of a gale-force Sirocco often occurs as a surface low moves into the Gulf of Gabes from Tunisia, combined with the passage of a deep
500 mb trough extending well into north
Africa and positioned west of the Gulf of Gabes. The gale-force Sirocco is most common during the spring and may reach wind forces between 5 and 8 Bft.